Elon Musk has offered to buy Twitter in a deal worth more than $43 billion and take the social media company private.

Musk’s best and final offer was to pay $54.20 per share for 100% of Twitter, and said that if his offer was not accepted he’d have to reconsider his position as a shareholder, according to an SEC filing.

Musk recently disclosed a 9.2% stake in Twitter, but he rejected an offer to join its board of directors and criticized the social media platform in tweets.

He wrote in the filing that he’d want to “transform” the social media platform as a private company.